This invention relates to an air fan, and more particularly to an air fan adapted to be received in a receiving housing of an electronic appliance to cool an electronic component.
Japanese Patent Application Laid-Open Publications Nos. 231940/1990 (2-231940) and 231941/1990 (2-231941) each disclose an air fan constructed so as to flow feed in a radial direction thereof perpendicular to an axial direction thereof by means of an axial fan. The air fan is generally called a radial fan in the art. An axial fan includes an impeller securely mounted on a revolving shaft of a motor. The impeller is provided with a plurality of blades and constructed so as to suck air on one of both sides defined in an axial direction of the revolving shaft of the motor and guide it toward the other side. Also, the impeller is arranged in a cylindrical cavity which is defined by a peripheral wall of a casing. The axial fan exhibits characteristics capable of increasing the amount of air fed while keeping a pressure at a reduced level. The radial fan was developed utilizing such advantageous characteristics of the axial fan. Thus, the radial fan exhibits characteristics capable of increasing the amount of air fed while being decreased in thickness or depth as compared with a cross-flow fan or a cirrocco fan and reducing noise as compared with a cirrocco fan.
The conventional radial fan described above is so constructed that the cavity in which the impeller is received is closed at one end thereof with a wall and provided with a lateral discharge port, which is formed by removing a part of a peripheral wall of the casing. The lateral discharge port is provided so as to thoroughly extend from one end of the cavity to the other end thereof, so that the blades of the impeller each are fully exposed from the lateral discharge port of the casing when it faces the port during rotation of the impeller.
The inventors made such a radial fan as described above utilizing the axial fan and conducted an experiment on the radial fan thus made. As a result, it was found that the radial fan causes the amount of air discharged from the lateral discharge port and blown against a component being cooled to be less than expected.
Also, when the conventional radial fan is received in a receiving housing of an electronic appliance decreased in thickness or depth, it causes the amount of air fed to be excessively decreased or rendered substantially zero.